Homework Help    Search   Site Map Biology      Physics      Chemistry      Maths     History    Links

Search  

Types of cells in our body.

Check out our latest service -Dictionary Of Computer Abbreviations (DOCA) today. Over 5000 words are there in our database.The largest free online computer abbreviation dictionary.


 


Cell is the structural and functional unit of life. It is a bit of protoplasm surrounded by a membrane.It is formed from pre existing cells. Protoplasm is a gel like material present inner to the cell membrane. Purkinje discovered protoplasm. Protoplasm is the physical basis of life. The jelly like material present inner to the cell membrane and outer to the nuclear membrane is called cytoplasm. It contains cell organelles. These cell organelles carry out all the activities of the cell and all these activities are controlled by the nucleus. Gel like material present inside the nucleus which contains chromosomes is called nucleoplasm. Chromosomes in the nucleus controls all the activities of the cell. They are made up of genes. Nucleoplasm is denser than cytoplasm but there are some organelles which fix in the nucleus in the proper position thus making it float on the cytoplasm. It is the endoplasmic reticulum which makes nucleus stable.

Cell is formed of pre existing cells. This theory is called 'Omnis Cellula Cellulae'. Total functioning of the cell is controlled by each and every cell. Animal cell lacks cell wall, vacuoles and chloroplasts. Vacuoles are very small and reconsidered absent.
Plant cell lack centrosomes. They help in cell division. In plants centrioles are directly formed without any chromosome and they control cell division. The rigid shape of a plant cell is due to the cell wall which is made up of cellulose. Cell wall is dead, provides protection and is freely permeable (it allows the easy passage of material).There are holes present on it. Cellulose is a type of carbohydrate made up of glucose. We cannot digest cellulose. The carbohydrate which we can digest is called starch.

Cell membrane is also called plasma membrane. It is present inner to the cell wall. In plant cell inner to the cell wall the protoplasm is covered by cell membrane or plasma membrane. In animal cell the cell membrane is the outermost covering. Cell membrane protects protoplasm. It is selectively permeable i.e., it will select the material which can be transported across the membrane.

Cytoplasm is present between nucleus and the plasma membrane. Its main component is water. It also contains some dissolved materials. Matrix is composed of water, some dissolved and some suspended material. It contains cell organelles.

Endoplasmic reticulum is a network of membranes connecting cell membrane and nuclear membrane. On its surface ribosomes may be present, then it is called rough endoplasmic reticulum if not present then it is called smooth endoplasmic reticulum. It acts as the cytoskeleton of the cell. It gives the cell the required shape. Intra-cellular transportation of material is carried out by it. It also stores fats, proteins and carbohydrates. Thousands of ribosomes are present in the cell. They are formed of smaller sub-units.they are granular and are not enclosed by any membrane. The function of ribosomes is to produce proteins. RNA determines the number of proteins.

Mitochondria are double membrane bound organelles called 'power house of the cell'. In the inner membrane there are several foldings or invaginations called cristae. All over this membrane oxysomes are present cristae increases surface area for more oxysomes. Oxysomes controls cellular respiration which produces ATP. It functions mainly as a compartment for aerobic respiration and ATP synthesis. It produces and stores energy. ATP (adenosine triphosphate) provides energy for all life activies.

Golgi complex consists of three structures. Cisternae are plate like structures present one over another. Vesicles are rounded or oval structures. Tubules are irregular shaped structures. Their main function is secretion and storage of carbohydrate, proteins and fats. Hydrolytic enzymes are present in lysosomes.These enzymes can digest the whole cell when the body is in severe starvation. They are also called suicidal bags of the cell. They protect the cell from any other organism which enters the cell. They carry out digestion of materials. If any complex material enters the cell then lysosomes convert it into simpler material and make it fit for use by the cell.

Centrosomes are present only in animals. Two centrioles are present inside the centrosome. Centrosome is present just outside the nucleus. It controls cell division and the genes are also controlled by centrosomes.

Plastids are present only in plant cells. They are of 3 types - chromoplasts (gives colours to the plant except green), leucoplasts(colorless plastid it stores food material) and chloroplasts (green coloured plastid). Their function is to perform photosynthesis. Chloroplasts are surrounded by two membranes. Inner to the inner membrane stroma is present. It contains several membrane plate like structures called thylakoid. They are arranged one over another to form grana. Thylakoid of the adjacent grana are connected by frets or lamella.

Nucleus is covered by two membranes and in between there are openings called nucleopore for the exchange of material.Inner to this membrane matrix is present which is called nucleoplasm. Inside the matrix thread like structures are present which are called chromatin or chromatin fibers. It contains genes to determine various characters to the organism. Chromatin are made up of DNA ( de-oxy ribonucleic acid) which controls all the characters of the organism. The pat of the DNA which is responsible of the production of one character is called gene. Like this several genes are present in several chromatin or DNA's. Chromatin are loose but they attain a definite shape by coiling this is called chromosomes. Two sets of chromosomes are present ,total 46, in which 23 are of father and 23 are of the mother.Chromosome is a hereditary material it goes from father or mother to the offspring.

Cell inclusions are dissolved or suspended in the cytoplasm. Carbohydrates are dissolved in different forms. Some of the carbohydrate are insoluble while some are insoluble. Carbohydrate forms a crystal like appearance called starch grains. Proteins form a crystal like appearance called aluerone layer. Fat is present in the form of fat globules. It is a reserved fat material present in the cytoplasm. We classify inclusions into 3 categories - reserved products, secretory and waste products. In case of banyan tree cystolith are present they are actually calcium carbonate crystals due to the excess of material. They are present lower surface of leaves.

In the case that you have a doubt on a something listed here or want to know something that has not been mentioned please use our Reference Boards .



Best Sites For Teachers
Teach Nology
Environment     Science News      Mesothelioma Information     Party Ideas    Funny Cats      Contact Us      Web Board  
Your Best BuyCool Unique Gift IdeasDiscount FurnitureInspirationPrivacy Policy Terms Of Use Credits
South Beach Extreme